Experimental and Numerical Analysis of Co2 and Ch4 Hydrate Formation Kinetics in Microparticles : A Comparative Study Based on Shrinking Core Model

The promotion of gas hydrate formation kinetics through mass transfer enhancement has been an important research topic, for which microparticles have been considered an effective method. In this work, carbon dioxide (CO2) and methane (CH4) hydrate formation kinetics in microparticles are investigated using “dry water” particles made of 3, 5 and 8-wt% silica. A modified shrinking-core model is established to study the CO2 and CH4 hydrates formation kinetics. It is the first model that integrates the effects of dissolved gas, the capillary effect of porous hydrate shell, and the volume change from water to hydrate. The experimental results show that “dry water” with 8-wt% silica represents the highest normalized gas uptake due to its smallest particle size. The simulation results demonstrate a reaction rate constant of 1.22×10–6 – 3.04×10–6 mol m–2 MPa–1 s–1 for CO2 and CH4 hydrate formation. Both the gas diffusion coefficient and the capillary effect decrease dramatically with the growth of hydrate. The water consumed through capillaries is more prominent in smaller particles, but it is less than 10% of water consumed at hydrate–water interface. Furthermore, a decoupled heat transfer model was developed to quantify the effect of heat transfer. The instantaneous temperature gradient in the hydrate shell is of the magnitude of 10–2 K m–1 , indicating that the impact of the heat transfer on hydrate formation kinetics is negligible. This work provides comprehensive insights into the process of gas hydrate formation in microparticles and contributes as a theoretical ground for gas hydrate kinetics improvement